The vortex dynamics and the self sustained tones in a plane jet impinging on a slotted plate

Abstract

Self-sustained tonal sounds are related to aero-acoustic coupling and occurs in impinging jets when a feedback loop is present between the jet exit and the impinged plate. The relation between the acoustic signal and the vortex dynamics should be understood in order to control the aero-acoustic coupling between the shear layer oscillation and the acoustic modes (self-sustained tones). In this study, a plane jet issuing from a rectangular nozzle and impinging a slotted plate is considered for different Reynolds numbers. Simultaneous measurements of the velocity and the acoustic fields were performed using respectively the time-resolved particle image velocimetry (PIV) and a microphone. The trajectories of the vortices are simultaneously investigated with the acoustic level. One single path was found for the vortices when the acoustic level was low. However, in the case of a peak in the acoustic level, two paths of the vortices can exist. A detailed illustration “step by step” of the convected vortices is presented simultaneously with the acoustic signal.